"The Flash" season 4 will feature the return of Gypsy (guest star Jessica Camacho) in this week's episode, introducing her to Earth-1's current meanie, Clifford DeVoe/The Thinker (Neil Sandilands). Barry Allen (Grant Gustin) will need every help that he can get, especially at this point where Team Flash has been repeatedly bested out by their enemy. However, in the villain's camp, The Thinker's closest confidante might have a change of heart after realizing how much of a monster the former has become.

According to the latest synopsis for "The Flash" season 4 episode 20, titled "Therefore She Is," Team Flash will cross paths once again with Gypsy, who has an important mission to accomplish in Central City. While Gypsy has some other business to deal with on Earth-1, Barry and his teammates can use her presence as an opportunity to foil The Thinker's latest plan. After all, Team Flash will need more meta allies to defeat the villain once and for all, knowing how powerful The Thinker has become after absorbing Ralph Dibny/Elongated Man's (Hartley Sawyer) power.

Meanwhile, "The Flash" season 4 episode 20 will also highlight the reunion of Gypsy and Cisco/Vibe (Carlos Valdes). The two have a lot of things to catch up on, and they probably have only limited time to figure out their future after dealing with The Thinker. Although, FanSided suggests that Gypsy's other reason for visiting Earth-1 is to convince Cisco in taking his father's place as the Breacher. 

Lastly, the viewers may witness an interesting development in the character of Marlize DeVoe (Kim Engelbrecht), The Thinker's wife. The mastermind, also known as The Mechanic, is the one responsible for the cybernetics technology that allowed her husband's consciousness to jump from one body to another. This time around, The Thinker will need Marlize's expertise to develop a new machine that will bring him one step closer to The Enlightenment. Unfortunately for Marlize, she will begin to feel her husband's cruelty towards her. Little by little, Marlize will see that her husband has never cared for anyone, including her, because the only important thing in his life is to become more powerful than ever.

"The Flash" season 4 episode 20 will air on May 1 at 8 p.m. ET on The CW.